1. Field of the Invention
The present invention relates to a mounted structural body having semiconductor chips or other electronic components mounted on a wiring board, and a method of manufacturing the same.
2. Background Art
Recently, electronic components are rapidly advanced in function, and reduced in size and weight. In the mounting method of semiconductor chips in package, too, demands for reduction of size, weight and thickness are increasing.
To solve the problems, as the technology for mounting semiconductor chips on the wiring board, the wire bonding technology is being replaced by the flip-chip technology of forming protruding electrodes on the surface of a semiconductor chip by using solder or gold wire, and connecting with the wiring board. The flip-chip technology is generally a technology of mounting a semiconductor chip on one side of a wiring board having a wiring pattern by way of protruding electrodes, filling the gaps of the semiconductor chip and the wiring board by pouring in a resin called under-fill, and fixing the semiconductor chip and the wiring board integrally. By this resin, the function surface of the semiconductor chip is protected, and a stable connection is realized.
Hitherto, as shown in FIG. 10A to FIG. 10D, a mounted structural body filled with a resin as under-fill has been generally known.
FIG. 10A to FIG. 10D are sectional views for explaining the resin injection method between the wiring board and the semiconductor chip of a conventional mounted structural body. In the mounted structural body, on pads 106 of wiring board 100 forming pads 106 and wiring patterns 161 at least on one side, semiconductor chip 104 is mounted on one side by way of solders 105. At this time, on wiring patterns 161 and the regions other than pads 106, insulation films 107, 171 made of resist or the like are formed.
First, as shown in FIG. 10A, using dispenser 108, resin 103 is injected from one position on the periphery where semiconductor chip 104 is mounted on wiring board 100. At this time, resin 103 spreads concentrically from dispenser 108 as indicted by dotted lines in FIG. 10B, and is injected into the gaps toward the outer circumference of semiconductor chip 104 as indicated by arrows.
Consequently, as shown in FIG. 10C, resin 103 is injected while spreading inside from the gaps between wiring board 100 and semiconductor chip 104.
As a result, as shown in FIG. 10D, the entire gaps between wiring board 100 and semiconductor chip 104 are filled with resin 103, which is cured, and then semiconductor chip 104 and wiring board 100 are integrally bonded.
In this method, the mounted structural body mounting the semiconductor chip on the wiring board is realized.
In this mounted structural body, however, steps are formed by wiring pattern 161 and insulation film 171, for example, or solder flux of non-cleaning type recently used for enhancing the productivity may be left over in the gaps as residues, and the flow of injected resin 103 may be partly disturbed and may be non-uniform. Accordingly, as shown in FIG. 10D, spaces 109 or voids not filled with resin 103 are left over, and the bond strength or peel strength may be reduced.
Besides, since resin 103 is injected from one position, as shown in FIG. 10D, region 110 not filled with resin 103 may be formed somewhere on the entire circumference of wiring board 100 and semiconductor chip 104. This is because resin 103 is injected concentrically as shown in FIG. 10B, and may not reach completely from the injection side to the opposite side end of semiconductor chip 104 due to presence of steps and residues. As a result, part of end or periphery of semiconductor chip 104 may not be bonded by resin 103, and semiconductor chip 104 may be peeled off or broken due to deformation stress from outside, or warp due to difference in coefficient of thermal expansion between semiconductor chip 104 and wiring board 100, and thereby the reliability may be lowered.
To avoid such inconveniences, Unexamined Japanese Patent Publication No. 2006-351559 (hereinafter called patent document 1) discloses a semiconductor chip mounting structure, in which a frame-like resin dam larger than the mounting area of a semiconductor chip is formed, and the under-fill resin is injected by a dispenser while moving on the circumference along one side of the semiconductor chip within this dam.
Further, Unexamined Japanese Patent Publication No. 2003-249603 (hereinafter called patent document 2) discloses an electronic device in which a frame-like step part having a recess smaller than the outer size of a circuit element is fixed on the surface of a board, and the confronting circumference of the circuit element and the step part is filled with a sealing resin.
However, in the semiconductor chip mounting structure of patent document 1, strict process conditions such as moving accuracy of the dispenser and stability of injection amount are needed together with complicated mechanism and equipment, and the productivity may be lowered.
According to the electronic device of patent document 2, it is only intended to realize a structure in which the sealing resin does not flow into the functional parts of the circuit element, and nothing is suggested about the structure of fixing between the opposite electronic component and wiring board by securely filling with under-fill resin, especially about the injection method.